CHEK2 and breast cancer: However, this widely discussed variant of CHEK2 – which seemed clearly associated with the predominance of breast cancer in western countries – was rarely detected in Asian populations, such as the Chinese (Song et al. 2006), Koreans (Choi et al. 2008), Japanese (Bell et al. 2007), Singaporeans (Lee & Ang 2008), Malaysians (Thirthagiri et al. 2009) and South Indians (Rajkumar et al. 2003).